Omron Industrial Automation examines how safety can be an enabler for increased productivity and reduced total cost of ownership.

There are few issues in machine design more emotive than safety, and it is a subject that becomes increasingly complex. Requirements are becoming more stringent and the numbers of people affected are increasing. Initially the safety of the operator during normal production was the primary focus of the machine safety system; however, it is now equally important to consider those tasked with maintaining, upgrading and repairing the machine throughout its entire life-cycle.

Performance and safety: opposing forces?

A traditional machine development project might start with the mechanical design, move on to the control systems design, and finish with the safety system. Some of the safety technologies employed might be more sophisticated, but conceptually this approach has moved forward very little. Pressures to improve machine performance with faster cycle times and reduce downtime have the potential to impact on safety, so is it possible to have a safe machine that operators can interact with more closely, or that engineers can repair or maintain perhaps without requiring a complete shut down and lengthy start up?

With traditional approaches to safety, the answer is frequently ‘no’, and this is often where incentives to defeat the safety system arise. The new safety standard – ISO 14119 – addresses this very issue. EN ISO 14119:2013, ‘Safety of machinery – Interlocking devices associated with guards – Principles for design and selection’, has now been harmonised to the Machinery Directive 2006/42/EC and superseded its predecessor, EN 1088. It specifies principles for the design and selection of interlocking devices associated with guards, and covers the parts of guards which actuate interlocking devices. In particular, it provides measures to minimise defeating of interlocking devices in a reasonably foreseeable manner

Traditional approach to safety system design is wrong

So why is the traditional approach to safety system design wrong? When you start with the mechanical system design, then move to the control system design, and only then look at developing the safety system in accordance with your risk assessment to conform with the Machinery Directive, then while you will probably have a safe machine, but not one optimised for performance. However, by taking a multi-disciplinary approach to safety, and make it integral to all aspects of the build, then there are huge opportunities to develop not only better safety systems, but also safety systems which are readily scalable from one machine to another.

Safety as an integral part of the machine automation platform

Considering safety right from the very beginning of the machine design project also helps to clarify thinking of what level of safety technology might be required. If only a few safety functions are needed, control built around a few safety relays may well be the most appropriate solution. For a greater number of safety functions, a standalone safety controller might provide the best option. Where the application involves a large machine or a complete production line, a safety PLC that looks and feels more like a conventional control product and which integrates more closely with the wider control system will probably be the best solution, offering the greatest number of safety functions through near-unlimited safety I/O.

This article was originally published in the Industrial Technology Magazine.  Go here for the full story